Some countries have roundabouts. Some countries let you make a right turn on a red light. Traffic law isn't any more universal than copyright law. All law is made up but that doesn't make it less real.
I always found it fascinating how universal copyright law is. Countries that can't agree on almost anything else have all deigned to give (okay, now that it's 2024, we can't use the rodent anymore, what's the new symbol of eternal copyright?) holy sanction for decades at a time.
Much of the heavy lifting is done by treaty-- not so much that anyone is asking legislatures directly to establish and extend copyright, but that it comes part-and-parcel with other international obligations.
Without the weight of such treaties, I wonder how many countries would do without an IP regime at all, especially if they don't see any IP-related export opportunities, so copyright and patent merely limits their ability to make cheaper versions of foreign goods.
I can drive my car over the land border between two countries and have to switch sides of the road. Or the speed limit can go up/down. Or they can mandate different safety equipment.
Copyright law is already different from country to country.